Display system cover

ABSTRACT

An assembly ( 16 ) for covering a visual display means ( 10 ) which has an array of pixels ( 12 ) is described. The assembly ( 16 ) comprises an array of cells ( 18 ) with reflective walls and an opening at each end. A transparent cover sheet ( 20 ) is positioned adjacent the open end of the cells ( 18 ) on one side of the array. The array is dimensioned such as in use each cell ( 18 ) is aligned with one pixel ( 12 ) of the visual display means ( 10 ). In this way, large visual display systems with excellent optical performance can be provided which can be used both internally and externally and are capable of bearing loads and forming structural members.

The present invention relates to an assembly for covering a visualdisplay system which improves the optical and physical performance ofthe system.

It is known to provide visual displays made up of an array of pixels,with each pixel being created by a light source such as an LED or theend face of an optical fibre. Such visual displays can be used forinformational signage, advertising, relaying TV pictures, artinstallations and so on. However, such displays suffer from a number ofdisadvantages. The angle at which the screen can be viewed and thedistance from which it can be viewed in order to see a reasonablycoherent and legible image are relatively limited. The opticalperformance and legibility even when viewed within the preferred rangesis not particularly great since the image tends to appear as dots ofcolour on a black background. The visual displays require additionalmodification, at great expense, in order to make them weatherproof foruse outdoors and such systems have limited loadbearing capacities andcannot be used as structural members.

It is also known to use an array of CRT, plasma or LCD screens coveredby thick glass sheets produce a large display. However, the size isstill limited and the overall image produced is disrupted by therelatively thick edges to the individual TV screens.

The present invention provides an assembly for covering a visual displaymeans which has an array of pixels, the assembly comprising an array ofcells with reflective walls and an opening at each end, and atransparent cover sheet adjacent the open end of the cells on one sideof the array, wherein the array is dimensioned such that in use eachcell is aligned with one pixel of the visual display means.

Preferably, the cells are contiguous and may be in the form of openended tubes. In a preferred embodiment, the cells are formed from ahoneycomb mesh of adjacent hexagonal cells. Alternatively, the cells maybe formed by a mesh with substantially square apertures. In a furtheralternative, each cell may comprise a parabolic reflector with anopening in the centre of the base for alignment with a pixel of thevisual display means. In a further alternative, each cell may comprise alight guide.

The walls of the cells may be provided with a surface treatment toincrease reflectivity.

Additionally, a lens may be provided in each cell to capturesubstantially all of the light from the pixel.

The cover sheet preferably comprises glass or plastic. The assembly mayalso comprise a bottom sheet to create a load bearing structure and mayalso provide a weather proofing capability to protect the visual displaymeans.

To improve the optical performance, the cover sheet may be moulded toform a lens aligned with each cell of the array. The cover sheet mayalso have a surface treatment applied to improve the opticalcharacteristics.

Further option to improve the optical performance is to include lensmeans between the array of cells and the cover sheet, aligned with thewalls of the cells, to allow diffusion of light between adjacent cells.The lens means may be in the form of adhesive used between the cells andthe cover sheet.

The present invention also provides a visual display system comprisingan assembly as described above secured to a visual display means havingan array of pixels, such that the array of cells is sandwiched betweenthe cover sheet and the visual display means.

In another aspect, the present invention provides a digital visualdisplay system comprising a plurality of discrete light sources arrangedin a plurality of rows, wherein the light sources in each row are offsetwith respect to the light sources in each adjacent row.

The invention will now be described in detail, by way of example only,with reference to the accompanying drawings in which:

FIG. 1 is a schematic cross sectional view of part of a first embodimentof the present invention in combination with a visual display means,along the line A-A in FIG. 2;

FIG. 2 is a schematic plan view of part of the first embodiment shown inFIG. 1;

FIG. 3 is a schematic plan view of part of a second embodiment of thepresent invention;

FIG. 4 is a schematic plan view of part of a third embodiment of thepresent invention;

FIG. 5 is a schematic plan view of part of a fifth embodiment of thepresent invention;

FIG. 6 is a schematic cross sectional view through part of a fifthembodiment of the present invention; and

FIG. 7 is a schematic cross sectional view of a further feature of theinvention, applicable to all of the embodiments.

FIG. 1 is a cross section through a first embodiment of the presentinvention in combination with a visual display means. The visual displaymeans 10 is of the dot-matrix (or digital) type, that is it comprises anarray of pixels 12 each of which is formed by a light source such as anLED or the end of an optical fibre. The pixels 12 are mounted on abacking element 14 as is well known in the art.

The assembly 16 of the present invention comprises an array of cells 18adjacent a transparent cover sheet 20. The walls 22 of the cells 18 areformed by a honeycomb mesh creating contiguous hexagonal cells as bestseen in the plan view of FIG. 2. The cells 18 are thus open at each end.The honeycomb mesh is typically formed of a material such as aluminium,thus making the walls 22 of the cells 18 reflective.

The array of cells 18 is dimensioned so that the assembly can be fittedover the visual display means 10 with each pixel 12 aligned with thecentre of one cell 18. Thus, light from each pixel 12 passes through acell 18 and can be observed through the transparent top sheet 20 by anobserver 24. Reflection from the walls 22 of the cells 18 helps tooptimise the amount of light transmitted through the cells 18, therebyenhancing the brightness of the image seen by the observer 24. The walls22 may have a surface treatment to improve their reflectivity.Additionally, lenses (not shown) may be incorporated into each cell 18to capture substantially all of the light from each pixel 12.

Employing the assembly 16 of the present invention in combination with avisual display means 10 provides a number of benefits. First, in termsof optical performance, internal reflection within each cell 18 meansthat the cells 18 are flooded with light. This in turn means the imageseen by the observer 24 comprises blocks of solid colour rather thandots of colour on a black background.

In addition, the viewing angle and viewing distance ranges areincreased. Thus, an observer may view the display from a greater rangeof angles and from a greater range of distances and still see a coherentand legible image.

A further advantage is that the top sheet 20 may be designed to providestructural performance, when combined with a bottom perforated sheet, tothe whole display unit, i.e. it may be a load bearing element, allowingthe unit to be used to create or form part of a floor or wall structure.

The top sheet 20 may also provide a weatherproofing function, allowingthe display system to be used externally without further modification tothe visual display means 10 itself.

The top sheet 20 may also be adapted to further enhance the opticalperformance by means of surface treatments and/or it may be moulded toform lenses (not shown) aligned with each cell 18 of the array toimprove the light output.

The cells 18 need not be hexagonal cells of a honeycomb structure asillustrated in FIGS. 1 and 2. The cells 18 may instead be formed ofcylindrical tubes 26, packed together as illustrated in FIG. 3.Alternatively, a mesh 28 with substantially square apertures could beused as shown in FIG. 4. Another arrangement is an array of equilateraltriangles as seen in FIG. 5. Another option is for each cell 18 to be inthe form of a parabolic reflector as seen in FIG. 6, having an openingin the centre of the base of each parabola to receive the pixel 12.

In some circumstances it is desirable to have some diffusion of lightbetween adjacent pixels. This enables the improved rendering of imageswhich have smooth edged forms or soft colour graduations. In order toallow for some diffusion between adjacent pixels, one option is toprovide a form of lens (30) on the top of the walls 22 of the cells 18,extending between the walls 22 and the cover sheet 20. This isillustrated in FIG. 7. This network of lenses may be created as aseparate part to be included in the assembly or may be formed by using aliquid adhesive, which sets into a light transmitting bead between thecells 18 and the cover sheet 20. This arrangement may be incorporated inany of the embodiments described.

A further possibility is to form each cell 18 as a light guide such as asolid glass or plastic element with a plane face at each end, whichallows substantially all the incident light to pass through withoutreflection, constituting the “open ends” of the cell. The side walls ofthe light guide which join these end faces, however, provide forsubstantially total internal reflection so that all the light enteringthe light guide is transmitted through it and out of the opposing endface.

It will be apparent from these examples of cells 18 are not exhaustiveand other possibilities exist.

As described above, the arrangement of pixels 12 and the shape andarrangement of the overlying cells 18 can take a variety of forms. Inparticular, the pixels 12 may be arranged in a square grid as shown inFIGS. 4 and 5 in which the pixels are in rows with the pixels in eachrow being aligned with the pixels in each adjacent row. Alternatively,the pixels 12 may be in an offset arrangement with the pixels in eachrow being offset with respect to the pixels in each adjacent row as inFIGS. 2 and 3. In some applications, this offset arrangement ispreferred since each pixel 12 has a greater number of equidistantneighbouring pixels 12. In the arrangements of FIGS. 2 and 3, each pixel12 will be equidistant from 6 neighbouring pixels 12. However, with thearrangement of FIGS. 4 and 5 each pixel has only four equidistantneighbours closest to it. The offset arrangement, with each pixel havinga greater number of equidistant neighbours, allows improved mapping ofimages onto the display and this results in images of better effectiveresolution to the observer.

Thus, the present invention makes it possible to provide large visualdisplay systems with excellent optical performance which are useableboth internally and externally and are capable of bearing loads andforming structural members. It will be apparent that a number ofvariations and modifications to the precise details described herein arepossible, without departing from the scope of the invention are set outin the claims.

1. An assembly for covering a visual display having an array of pixels,the assembly comprising an array of cells with reflective walls and anopening at each end, and a transparent cover sheet adjacent the openends of the cells on one side of the array, wherein the array isdimensioned such that each cell is aligned with one pixel of the visualdisplay.
 2. An assembly as claimed in claim 1, wherein the cells arecontiguous.
 3. An assembly as claimed in claim 1, wherein each cellcomprises a tube open at each end.
 4. An assembly as claimed in claim 1,wherein the array comprises a honeycomb mesh creating adjacent hexagonalcells.
 5. An assembly as claimed in claim 1 wherein the array comprisesa mesh with substantially square apertures.
 6. An assembly as claimed inclaim 1, wherein each cell comprises a parabolic reflector having anopening in the centre of the base for alignment with pixel.
 7. Anassembly as claimed in claim 1, wherein each cell comprises a lightguide.
 8. An assembly as claimed in claim 1 wherein the walls of thecells are provided with a surface treatment to increase theirreflectivity.
 9. An assembly as claimed in claim 1 further comprising alens in each cell.
 10. An assembly as claimed in claim 1, wherein thecover sheet comprises glass or plastic.
 11. An assembly as claimed inclaim 1, further comprising a bottom sheet to create a load bearingelement.
 12. An assembly as claimed in claim 1, wherein the cover sheetprovides weather proofing to the visual display means.
 13. An assemblyas claimed in claim 1, wherein the cover sheet is shaped to form a lensaligned with each cell of the array.
 14. An assembly as claimed in claim1, wherein the cover sheet is provided with a surface treatment toimprove the optical performance.
 15. Assembly as claimed in claim 1,further comprising lens means arranged between the array of cells andthe cover sheet, aligned with the walls of the cells, operable todiffuse light between adjacent cells.
 16. An assembly as claimed inclaim 15, wherein the lens means is provided by adhesive between thecells and the cover sheet.
 17. A visual display system, comprising: avisual display having an array of pixels; a cover assembly secured tothe visual display, the cover assembly having an array of cells withreflective walls and an opening at each end, and having a transparentcover sheet adjacent the open ends of the cells on one side of thearray, the array of cells being configured such that each cell isaligned with one pixel of the visual display and configured such thatthe array of cells is sandwiched between the cover sheet and the visualdisplay.
 18. A digital visual display system comprising a plurality ofdiscrete light sources arranged in a plurality of rows, wherein thelight sources in each row are offset with respect to the light source ineach adjacent row.